One application of such pipe break valve devices is in heavy trucks having a plurality of axle lines, the pipe break valve units acting as pilot switching valves on the axle balancing cylinders. The axle balancing cylinders are installed movably, so that a flexible line, in particular a high-pressure hose piece, is inserted as a supply line for the flow medium, for example hydraulic oil, upstream of the cylinder. The throttle device has the effect that pressure changes briefly occurring abruptly, for example on account of unevennesses in the road, do not cause the valve to close. Furthermore, the throttle device has the effect that, when a persistent differential pressure occurs between the inlet connection and the outlet connection, which happens, for example, when a hose bursts, the pipe break valve shuts off passage sealingly as a result of the corresponding transverse movement of the valve slide.
FIG. 5 illustrates diagrammatically in cross section a known pipe break valve device 60 of the applicant. The pipe break valve device 60 has a housing 62 which in FIG. 5 possesses an inlet connection 64 on the underside and an outlet connection 66 on the top side. The two connections 64, 66 are in communication connection inside the housing 62, the flow direction of the medium, for example hydraulic oil, being identified in FIG. 5 by the arrow F.
In the housing 62 there is a continuous transverse bore 80, within which a valve slide 68 is mounted displaceably in the transverse direction Q. In each case on the left and on the right of the valve slide 68 there is a sealed-off oil space 70.1, 70.2 which is in communication connection with the flow cross section of the housing via throttle ducts 74, in each case both with the inlet connection region and with the outlet connection region. The first duct region of the throttle ducts has a very small bore cross section which ultimately gives rise to a throttle effect. Inside the oil spaces 70.1, 70.2 there are in each case elastic means 72.1, 72.2 which act on the valve slide 68 and, in the normal operating state, hold it in the open state.
In the normal operating state, both oil spaces 70.1, 70.2 are filled correspondingly with hydraulic oil and, as already mentioned, are in communication connection with the interior of the flow cross section. The rigidity of the elastic means 72.1 and 72.2 is in this case set such that, if a pressure difference occurs when the flow medium flows through the housing 62, the valve slide 68 is in the open position.
The throttle ducts 74.1, 74.2 and oil spaces 70.1, 70.2, in conjunction with the elastic means 72.1, 72.2, constitute a throttle device which prevents the valve from shutting off in the event of a pressure peak briefly occurring suddenly, since the filling state of the oil spaces 70.1, 70.2 does not change substantially on account of the given throttle action, and therefore the valve slide 68 is held in its position. If, then, for example, a line break occurs on one side, that is to say a situation where a pressure difference between the inlet region and outlet region is present for a relatively lengthy period of time, oil flows via the throttle duct 74.1 into the right oil space 70.1 (arrow F1) and at the same time oil flows out of the left oil space 70.2 via the throttle ducts 74.2 into the outlet region (arrow F2), thus giving rise ultimately to a displacement of the valve slide 68 to the left, the valve slide 68 shutting off the throughflow after a stipulated displacement travel is reached. The valve slide 68 executes a displacement movement to the left when the line connected on the top side breaks. If the line connected on the underside breaks, the valve slide 68 executes a displacement movement to the right in the transverse direction Q in order to shut off the throughflow.
The known pipe break valve device ensures permanently reliable functioning. The relatively complicated structural set-up, the multiplicity of components and the complex geometry necessitate a high outlay, and therefore, in terms of economical production, high costs are incurred which have to be reflected in the price.
DE 10 2009 043 568 A1 describes a hydraulic safety valve for shutting off a first duct, connectable to a pump, with respect to a second duct, connectable to a hydraulic consumer. In this case, two coaxially arranged separate blocking pistons are mounted displaceably in the axial direction, are acted upon in each case by the spring force of a spring and can be transferred, counter to the spring force of the respective spring, from an open position into a blocking position as a result of the overshooting of a flow velocity of the hydraulic medium and of a pressure difference thereby occurring. The ducts are shut off by means of this movement. In this case, there is a damping device for the damped or time-delayed closing of the blocking pistons. The damping device is designed as a chamber which is in communication connection with the fluids via a throttle bore. The throttle chamber therefore necessarily has to be vented. For this purpose, corresponding venting ducts are provided which can be closed and, if required, opened by means of screws. On account of the chosen design, it is necessary that sealing means are present between the inner wall of the blocking piston and the inner wall of the housing. These sealing means which are present may present problems, since, if not actuated for a lengthy period of time, they may seize up due to ageing influences and may be able to therefore no longer ensure their functioning when required. Since this safety valve necessarily has to be vented, it is necessary to ensure, for example on a vehicle, a straightforward situation where the installed safety valve is accessible in order to carry out venting.
German Utility Model specification DE 20 2011 050 667 U1, published at a later date, relates to a hydraulic pipe, line or hose break safety shut-off valve for shutting off a supply line duct, connectable to a pump, with respect to an outflow line duct, connectable to a hydraulic consumer. The supply line duct and outflow line duct issue into an axial bore, extending in the direction of an axial axis, of a valve housing, in which axle bore is mounted displaceably a blocking piston which is acted upon in the axial direction by spring force of a spring, with the result that the blocking piston is held in an open position up to a specific limit flow velocity of a hydraulic medium which amounts to a value greater than zero. Here too, a separate damping chamber is connected via throttle ducts and has to be vented via ventilation ducts in order to ensure permanently reliable functioning. The set-up of this valve is relatively complicated and therefore cost-intensive. Moreover, even here, it is absolutely necessary that sealing means are present between the outer wall of the moveable blocking piston and the inner wall of the housing, these sealing means possibly entailing the problems already described above.
German Laid-Open Publication DE 2 352 826 discloses a hydraulic pipe break valve closing in a damped manner, with a blocking piston, held open by a compression spring, between a consumer connection and a connection leading to the pump and return. In this case, via a relatively complicated duct system, a damping space is in communication connection with the space of the blocking piston by means of a member which reduces the throughflow cross section of at least one bore under the action of a pressure drop building up between the connections and displacing the blocking piston counter to the action of the compression spring, after this displacement has commenced. The damping action is consequently adjustable. This valve also has a highly complex set-up and, in terms of economical use, can therefore be used to only a restricted extent.
U.S. Pat. No. 6,513,545 B2 discloses a nonreturn valve, in particular suitable for gas lines, in which a set screw is used which acts on a spring in order to set the spring force of the latter and therefore its recoil characteristic. This valve device has no damping properties of any kind and is therefore unsuitable for the use of the pipe break valve device according to the application, for example in heavy motor trucks, since it is not capable of maintaining “permissible” pressure fluctuations while at the same time continuing to fulfill its function.
U.S. Pat. No. 3,995,656 describes a valve for a high-pressure gas line which is designed as a regulating valve and does not present any safeguard against a hose break. Moreover, this valve also has no damping properties.
U.S. Pat. No. 5,507,466 discloses a valve device which is capable of shutting off the valve automatically after a stipulated fluid volume has flowed through. The valve slide employed for this purpose is mounted longitudinally displaceably and is located within a continuous recess. By means of a valve of this type, it is possible to carry out metering of a volume. As soon as this volume is reached and the consumer-side port is closed, the valve slide moves back into its initial position, since it is under the action of a spring force, and is then in the open state, in order once again to dispense a stipulated volume quantity, as required. As soon as the valve slide is stationary, for example as a result of the shut-off of the outflow duct, it moves back into its initial position. Here too, sealing means are arranged between the outer wall of the valve slide and the inner wall of the housing in order to ensure permanently reliable functioning. The valve illustrated contains a relatively large number of additional components and also ensures a nonreturn function, that is to say, if high flow velocities suddenly occur, closing is initiated by the valve slide.
U.S. Pat. No. 2,699,799 describes a nonreturn valve in which the valve slide is under the influence of a spring force and is arranged within a continuous recess in the housing. This valve automatically ensures throughflow under low pressure in one of the directions and shuts off as soon as a pipe pressure prevails in the other direction.
EP 1 672 259 A1 discloses a safety valve in which a valve slide is present longitudinally displaceably within a continuous recess. The valve slide is under the action of a spring force which is arranged in a damping chamber. The damping chamber influences the displacement travel of the valve slide under specific preconditions. The valve slide itself is sealed off with respect to the inner wall of the housing of the valve via special sealing elements. Here too, because of the sealing elements present, there is the problem regarding permanently reliable functioning, in particular regarding non-actuation of the valve slide which lasts for a relatively lengthy period of time, which may influence the action of the sealing means and, in particular, required friction values which are to ensure functioning are no longer available, so that, overall, functionality as required is then no longer ensured.